As biologic drugs increase in popularity, parenteral delivery devices are expected to be widely used. Injection drug delivery devices, such like the autoinjector, can ease medication preparation/administration and reduce needle injury, which results in improved patient convenience and compliance. Due to the advantages mentioned above, more patients and healthcare professionals prefer automatic injection devices to the traditional manual syringes. Many devices of the above mentioned type allowing a patient to self-administer one or more (generally two) doses of a medicament are known. U.S. Pat. No. 6,575,939 discloses an autoinjector device comprising a syringe housed in a casing formed by an inner part and an outer part capable of sliding in relation to each other. This autoinjector allows a single dose of medicament to be administered. EP Pat. No. 700307 discloses a two-dose autoinjector allowing the automatic delivering of a first dose of a medicament and the manual administration of a second dose. An autoinjector of this type is commercially available under the trade mark Twinject® and allows the first dose to be administered automatically, but the second dose must be manually administered. U.S. Pat. No. 8,961,463 describes an auto-injector that allows the end-user to self administer first and second doses of a medicament. However, the actuation mechanism for delivering the first and second doses are quite different and the mechanism cannot be applied for delivering more than two doses.
Another popular type of injection device is a pen injector. Such pen injector devices may contain a dose metering mechanism that administers a dose based on end-user selection. These devices are capable of delivering multiple doses. As for pen injectors, a lead screw or rotating plunger is provided which is mechanically coupled to a dose-setting knob or other actuator through a series of mechanical connections. The typical pen injector mechanism is fairly complex and consists of multiple cooperating parts. The pen injector design mechanism also limits the maximum delivery volume (normally less than 0.5 mL). For the reasons of cost and simplicity of use, a minimum number of working parts is desired.
It would be an improvement in the art, therefore, to provide a multiple use autoinjector for the automatic injection of a medicament, which is user-friendly and is easier to manufacture as compared to the conventional devices.